Method for the preparation of mixed base greases



United States Patent M METHOD FOR THE PREPARATION OF MIXED BASE GREASES Eric 0. Forster, Hillside, N. J assignor to Esso Research and Engineering Company, a corporation of Delaware Application July 28, E52, Seriai No. 301,194

7 Claims. (Cl. 252-39) This invention relates to lubricating grease compositions. Particularly the invention relates to lubricating grease compositions having outstanding structural stability and high temperature performance. More particularly, the invention relates to a lubricating grease composition having excellent all-purpose utility which comprises a lubricating oil thickened to a grease consistency with a complex of a calcium soap and a soap selected from the class consisting of barium, strontium and magnesium which is prepared by a sequence of specific processing steps.

The preparation of calcium base greases is old in the art and is well described by the patent literature. Such greases are excellent in structure, water resistance and appearance. However, the high temperature properties of calcium greases are very poor. This is due to the necessity of incorporating water with the calcium soaps during the manufacture of calcium soap greases. At temperatures above about 200 F. the water of formulation is driven off and the grease structure breaks down.

It has now been found, and forms the object of this invention, that a calcium base grease having all the advantages of Water resistance and characteristic structural stability of the calcium greases and having, in addition, excellent high temperature properties may be prepared by combining with the calcium soap of the prior art varying amounts of a soap of a metal selected from the group consisting of magnesium, barium and strontium. It is to be especially noted that there are certain steps in the manufacture of the grease compositions of invention which must be carried out in order for the resulting product to have the desired properties. These are, briefly, the dispersal of the calcium soap portion of the thickening agent prior to the dispersal of the other soap, and heating the mixture of soaps and oil to a temperature in excess of 350 F. during the preparation. These steps will be explained in more detail below.

The lubricating oil which is utilized as a dispersant for the soaps in preparing the greases of the invention may be selected from a wide variety of lubricating oils. A mineral lubricating oil preferably of naphthenic origin may be chosen as the grease base. It should have a viscosity within a range of from about 40 SUS at 100 F. to about 4000 SUS at 100 F. As in the preparation of most grease compositions, the mineral oil chosen should be that lubricating oil which would be used to furnish proper lubrication if a liquid oil could be used. It is preferred to use a mineral oil having a viscosity of from about 300 to 1500 SUS at 100 F. to formulate the greases of this invention.

Although a mineral lubricating oil, such as a conven: tionally refined distillate, is preferred for the preparation of the improved greases of invention, a synthetic oil may also be utilized as the dispersing'agent. Although a synthetic lubricant of the ester type, for example, the esters of dibasic acids and long chain alcohols, is a preferred type, other well known synthetic lubricants may be used. Complex esters made from dibasic acids, glycols, and alcohols may be used as may the polymerized glycol 2,708,659 Patented May 17, 1955 esters, glycol ethers, polymerized olefins, alkylated aromatics, polymerized silicones, formals, mercaptals, and the like. The only prerequisite is that the dispersant chosen be one that will furnish the desired lubrication when utilized as a grease composition.

The acid used to form the soaps that are used in formulating the greases of invention may be any of the high molecular Weight fatty acids commonly used in grease making. Such fatty acids as the hydrogenated fish oil acids, stearic acid, oleic acid, hydroxy acids, tallow, any of the generally known fatty acid glycerides or mixtures of these in any proportions may be used. The acids prepared by the Oxo process having from 10 to 30 carbon atoms may also be used. of the high molecular weight fatty acids the preferred embodiment contemplates the use of the hydrogenated fish oil acids.

As was stated above, the thickening agent used in formulating these new and improved greases is a mixture of calcium soap and a soap of a metal selected from the group consisting of barium, strontium and magnesium. The calcium soap must be present in amounts ranging from about 2.5% to about 15.0% by weight, based on the weight of the finished composition. The amount of the soap of the other metal used is such that the molar ratio of the calcium soap to the second metal soap is between 8:1 to 1:8 with a mol ratio within the range of 2:1 to 1:2 being especially preferred. The amount of the combined soaps present will depend somewhat upon the desired final consistency of the product. Ordinary usage would call for a grease composition according to the instant invention containing from about 5% to 30.0% by weight of combined soap, with a range of from 10.0% to 20.0% of soap being especially preferred.

In addition to the two critical limitations outlined above, that is, use of a combination of calcium soap with limited amounts of a barium, strontium, or magnesium soap of a high molecular weight substantially saturated fatty acid as the thickener, there are two other process limitations which must be met in preparing the grease compositions of this invention. It is an essential feature in the preparation of these grease formulations that the calcium soap be dispersed in the lubricating oil base before the other metal soap is added and dispersed. The exact reason for this phenomenon is not known, but it is believed that the calcium soap increases the solubility and hence improves the degree of dispersion of the other metal soap in the oil and thus increases the yield as well as the structural stability of the finished product.

The second critical feature in the method of formulation is that the total mixture of oil and soap must be heated to a temperature above about 350 F. after dehydration. It is believed that a phase transition of the soap mixture occurs at or above 350 F. producing a EXAMPLE I In accordance with the concepts of the instant invention but without heating above 350 F. the following grease composition was prepared by the procedure given below:

Formulation I I. 17.00% hydrogenated fish oil acids (Sap. No. 195) 0.88% calcium hydroxide 5.63% barium hydroxide octahydrate 76.49% mineral oil distillate SUS/210 F.)

TABLE H Efiect 0 mol ratio and acidity 'on the penetration and dropping point of calcium-barium greases Acid Grease M01 Ratio Example Number Calclum- Dr in Penetra Barium opp g tion' Point (mm I at Number e (Percent 77 leic) Alkaline Grease ASTM gp g 3g2? NNeug.

o um er F.) 9 at (Percent NaOH) After 10,000 strokes in grease worker using fine hole plate.

Inspection of the data in Table II indicates that any amount of barium soap added to a calciumsoap in the course of grease manufacture will improve the high temperature qualities and structure stability of the final product. Although small amounts of barium soap will cause substantial improvements, the most marked appear when the mol ratio of calcium to barium is smaller than 8:1, i. 2. 4:1 or 2:1, etc. Thus, following the ultimate uses contemplated, the grease composition can be varied in such a manner as to meet a large variety of specification requirements.

The fact that changes from acidic to alkaline reacting grease compositions do not affect to any appreciable ex.- tent the finished product adds to the desirability of this composition and cases the control of manufacturing procedures.

The data of Table H above are shown graphically in the accompanying drawing. In the drawing, the dotted line represents the dropping points and the solid line depicts the penetrations of the greases of Examples VII through X. It is clearly seen from this drawing that the soap combination of the grease of invention imparts desirable properties of high temperature stability and overall structural stability.

What is claimed is:

1. A process for the preparation of lubricating grease compositions having outstanding water resistance and high temperature properties which comprises the steps of dispersing in the presence of water from about 2.5% to about 15.0% by weight, based on the weight of the final grease composition, of a calcium soap of a high molecular weight fatty acid in a lubricating oil, subsequently dispersing a second soap selected from the group consisting a barium, strontium and magnesium soaps of high molecular weight substantially saturated fatty acids in said mixture in amounts such that the mol ratio of said calcium soap to said second soap is from 8:1 to 1:8, and heating the resulting mixture up to a temperature of about 250 F. to dehydrate said resulting mixture, subsequently heating to a temperature between about 350 to 420 F. and cooling the resulting composition.

2. A process according to claim 1 wherein from 5% to 30% by weight of total soap is utilized.

3. A process according to claim 1 wherein said mol ratio of calcium soap to said second soap is from 2:1 to 1:2.

4. A process according to claim 1 wherein said second soap is barium and wherein said mol ratio of said calcium soap to said barium soap is 2:1 to 1:2.

5. A process according to claim 1 wherein said second soap is strontium.

6. A process according to claim 1 wherein said second soap is magnesium.

7. A process for the preparation of lubricating grease compositions having outstanding water resistance and high temperature properties which comprises the steps of dispersing in the presence of water from about 2.5% to about 15.0% by weight, based on the weight of the final grease composition, of a calcium soap of a high molecular weight fatty acid in a lubricating oil, subsequently dispersing a second soap selected from the group consisting of barium, strontium, and magnesium soaps of high molecular weight substantially saturated fatty acids in said mixture in amounts such that the mol ratio of said calcium soap to said second soap is from 8:1 to 1:8, heating the mixture up to a temperature of about 250 F. to dehydrate said mixture, subsequently heating to a temperature within a range of about 380 to 420 F., and cooling the resulting composition.

References Cited in the file of this patent UNITED STATES PATENTS 2,070,781 Brunstrum et a1 Feb. 16, 1937 2,389,523 Lcyda Nov. 20, 1945 2,409,950 Meyer Oct. 22, 1946 2,417,429 McLennan Mar. 18, 1947 

1. A PROCESS FOR THE PREPARATION OF LUBRICATING GREASE COMPOSITIONS HAVING OUTSTANDING WATER RESISTANCE AND HIGH TEMPERATURE PROPERTIES WHICH COMPRISES THE STEPS OF DISPERSING IN THE PRESENCE OF WATER FROM ABOUT 2.5% TO ABOUT 15.0% BY WEIGHT, BASED ON THE WEIGHT OF THE FINAL GREASE COMPOSITION, OF A CALCIUM SOAP OF A HIGH MOLECULAR WEIGHT FATTY ACID IN A LUBRICATING OIL, SUBSEQUENTLY DISPERSING A SECOND SOAP SELECTED FROM THE GROUP CONSISTING A BARIUM, STRONTIUM AND MAGNESIUM SOAPS OF HIGH MOLECULAR WEIGHT SUBSTANTIALLY SATURATED FATTY ACIDS IN SAID MIXTURE IN AMOUNTS SUCH THAT THE MOL RATIO OF SAID CALCIUM SOAP TO SAID SECOND SOAP IS FROM 8:1 TO 1:8, AND HEATING THE RESULTING MIXTURE UP TO A TEMPERATURE OF ABOUT 250* F. TO DEHYDRATE SAID RESULTING MIXTURE, SUBSEQUENTLY HEATING TO A TEMPERATURE BETWEEN ABOUT 350* TO 420* F. AND COOLING THE RESULTING COMPOSITION. 